MST Cluster Hierarchy for Inter-Cluster Load Balancing

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Solution Overview

Problem

IEEE Std. 802.1Q-2005 multiple spanning tree protocol (MSTP) limits load balancing across MST region boundaries, preventing efficient utilization of network bandwidth and requiring traffic to be contained within MST regions, which presents a single logical entity to external nodes but restricts load balancing between internal and external nodes.

Innovation Solution

Introducing an additional level of hierarchy called MST clusters within the MST environment, where a MST cluster is defined within a MST region, allowing nodes to present themselves as a single logical entity while enabling per-MSTI load balancing across inter-cluster links, using modified BPDUs that include a CIST Cluster Root Identifier and MSTI Cluster Configuration Messages to manage traffic within and across clusters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If MST regions present a single logical entity to external nodes, then traffic containment within the region is achieved, but load balancing across region boundaries is prevented

Engineering Contradiction:
Improvetraffic containmentVSAvoidload balancing
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent segments the MST region into multiple MST clusters, each capable of independent load balancing operations. This segmentation allows internal traffic containment within clusters while enabling load balancing across multiple inter-cluster links to external nodes, resolving the contradiction between single-logical-entity presentation and multi-link load balancing capability

Inventive Principle:
Principle #1Segmentation

2Quantity of substance

If multiple links interconnect MST region with external nodes, then network bandwidth is available, but only a single link is utilized due to MST region limitations

Engineering Contradiction:
Improveavailable bandwidthVSAvoidlink utilization
Core Design Contradiction:
Quantity of substanceVSProductivity

Solution Approach 1:

The patent introduces dynamic load balancing within MST clusters by allowing different MSTIs to dynamically select different inter-cluster links based on traffic demands and link conditions. This dynamic behavior enables multiple links to be actively utilized for load balancing while maintaining the MST region's single logical entity appearance to external nodes

Inventive Principle:
Principle #15Dynamics

Data Source

PatentUS10212074B2Level of hierarchy in MST for traffic localization and load balancing
Publication Date: 2019.02.19 CISCO TECHNOLOGY INC
  • US10212074B2 patent drawing
  • US10212074B2 patent drawing
  • US10212074B2 patent drawing

AI summary

In one embodiment, a multiple spanning tree (MST) region is defined in a network, where the MST region includes a plurality of network nodes interconnected by links. A MST cluster is defined within the MST region, where the MST cluster includes a plurality of network nodes selected from the plurality of network nodes of the MST region. A network node of the MST cluster generates one or more MST bridge protocol data units (BPDUs) that present the MST cluster as a single logical entity to network nodes of the MST region that are not included in the MST cluster, yet enables per-multiple spanning tree instance (per-MSTI) load balancing of traffic across inter-cluster links that connect network nodes included in the MST cluster and network nodes of the MST region that are not included in the MST cluster.